Fuse constructions



Jan. 28, 1958 J. M. WALLACE 2,321,604

' FUSE qonsmucnons S 4 Sheets-Sheet 1 Filed Nov. 29. 1952 WITNESSES:INVENTOR 9/ 1 LX James M. Wallace %1/ (F1; @(r 4 WW ATTORN Jan. 28 1958u, M. WALLACE FUSE consmuc'nons Filed Nov. '29. 1952 INVENTOR James M.Wallace Material ATTORNEY strain-wire construction, which r 2,821,604Ice Patented Jan. 28, 1958 FUSE CONSTRUCTIONS James M. Wallace,Montclair, N. J., assignor to Westinghouse Electric Corporation, EastPittsburgh, Pa., a corporation of Pennsylvania Application November 29,1952, Serial No. 323,185 2 Claims. (Cl. 200135) 'IIhis invention relatesgenerally to circuit-interrupting devices, and more particularly, tofusible interrupting devices adapted to automatically interrupt acircuit upon the passage therethrough of currents of a predeterminedmagnitude.

-A primary object of my invention is to provide an improved fusibleinterrupting device which will be more economical to manufacture thanthose heretofore used in the industry, and, more important, which willbe more effective and eflicient in operation.

A more specific object of my invention is to provide a novel fuse linkwhich will have an improved strain-wire construction.

It is well known in the art to parallel the fuse, in a fusibleinterrupting device, with a strain wire, the latter havlng a relativelyhigh tensile strength to hold in tenslon a retracting spring, fuseterminals upon the fusion thereof. The retracting spring, which is undertension, rapidly separates the fuse terminals and sobrings about agreater contact of the es- .tablished are within the interior of anenclosing tube, within which the fusible device is housed. Generally,the interior walls of the housing or fuse tube evolve anarcextinguishing gas upon contact with the arc drawn upon fusion of thedevice.

Since the tensile strength of the fuse itself is relatively low, it iscommon practice to relieve the fuse of such tensile stresses by theemployment of the parallel-disposed strain element, the latterfurnishing the high tensile strength required to maintain the retractingspring under tension.

Prior art constructions of this type have been rendered ineffective andsubject to faulty operation by the strain elements breaking under normalconditions due to mechanical failure, or being improperly secured to thefuse terminals. Since fusible devices are a high quantity" productionitem, it is necessary to provide a construction adapted for rapidassembly, and which will make allowance forany errors which may occurduring the assembly ,operation by the human factor. Accordingly, it is afurther object of myinvention to provide an improved not only will beeffective, maintain its tensile strength, avoid the possibility of being.misassembled, but will also be economical to manufacture.

out, depicted in the fused condition;

Fig. 2 is an enlarged, fragmentary, vertical sectional view through theopen-link fuse employed in the construction illustrated in Fig. 1;

Fig. 3 is a view taken at right angles to Fig. 2; Fig. 4 is an enlargedview of the fuse proper of Fig. 3,

:to more clearly indicate the method of attachmentof myimproved strainclip; Fig. 5 is a plan view of the strain clip in blank form;

which serves to separate the Fig. 6 is a side elevational view of thestrain-clip blank after preforming operations have taken place;

Fig. 7 is an end view of the strain clip of Fig. 6;

Fig. 8 is a plan view of the fuse proper;

Fig. 9 is an edge view of the fuse shown in Fig. 8;

Fig. 10 is a vertical, sectional View through a fuse holder havingtherein a fuse-refill unit incorporating features of my invention; 7

Fig. 11 is an enlarged sectional view of the fuse-refill unit employedin the fusible interrupting device of Fig. 10;

Fig. 11A is a plan view of the strain-clip blank employed in this formof my invention; and

Fig. 12 is a view similar to Fig. 11, but shown at right angles thereto.

Referring to the drawings, and more particularly to Fig. 1 thereof, thereference numeral 1 generally designates an open-link cut-out employingmy invention, and

shown in the fused condition. The cut-out 1 includes a support insulator2, preferably composed of a suitable weather-proof material, such asporcelain or the like, which is supported in a substantially verticalposition as shown,'by a mounting plate 3. The mounting plate 3v issecured to any suitable support, such as a cross-bar associated with thetop of a distribution pole, not shown.

Secured by a support 5 at the upper end of the insulator 2 is an uppercontact arm 6, preferably formed of a suitable resilient wire, such as aPhosphor bronze wire. The contact arm 6 is, therefore, inherentlysomewhat resilient, and serves to support, in a return bend 7 thereof,the eyelet 8 of an open-link fuse, generally designated by the referencenumeral 10.

Clamped by a clamp 11 to a support plate 12, at the lower end of theinsulator 2, is a lower or bottom contact arm assembly 13. The contactarm assembly'13 is formed of wire, preferably resilient and preformed asshown. Again the wire is preferably Phosphor bronze, and the free end ofthe arm 13 has a return bend 14, which securely holds the lower contactbutton 16 of the open-link fuse 10.

As well known by those skilled in the art, the openlink fuse 10 ismounted in place by the usual hook stick, one prong of which is insertedwithin the upper loop 17 of the fuse link 10, so that the contact button16 may be guided into position within thereturn bend 14. When this isdone, the further upward movement of the hook stick causes the helicalspring 18, integrally formed with the arm 13, to be moved into tensionat the same time that the loop 17 is raised upwardly into positionwithin the return bend 7 of the upper contact arm 6.

Upon the occurrence of 'a short-circuit condition in the line connectedto the terminals 19, '20, the fuse link 10 will fuse and the lower cable21 will be released'to permit the lower contact arm 13, under thetension of the spring 18, to withdraw the fuse remnants out of the fusetube 22, thereby extinguishing the arc and breaking the circuit. Whenthis occurs, a maintenance man must remove the loops 17, 17a from thecontact arms 6, l3 and replace the spent fuse link 10 with a new fuselink.

Figures 2-9 more clearly show the internal construction of the open-linkfuse 10. Referring to these figures, with particular attention beingdirected to Figs. 2 and 3 thereof, it will be noted that the fuse tube22 is of composite con struction, the tube 22 comprising an outer tube22a formed of a weather-proof material, such as a suitable phenoliccondensation product, and an inner tube 22b, which is preferablycomposed of a gas-evolving material, such as fiber. 1

Disposed at the upper end of the fuse tube 22 is a cap 23, which ispreferably soldered to the upper cable 24. Hence, the cap 23 closes theupper end of the fuse tube 22 to prevent rain or snow entering therein.

Secured, as by soldering, to the lower end of the "conducting cable 24,constituting a fuse terminal 25, is a strain clip 26, the configurationof which is more clearly shown in Figs. 5-7 of the drawings.

Preferably the strain clip 26 is stamped from sheet material into blankform, as indicated in Fig. 5. Preferably the strain clip is formed of ahigh-resistance material having the requisite mechanical strength, suchas material being a copper-nickel alloy, for example.

Following the blanking operation producing the clip, as shown in Fig. 5,preforrning operations are manipulated to result in the strain clip 26assuming the configuration as shown in Figs. 6 and 7. V

It will be observed that the strain clip 26 has an intermediatelydisposed strain strap portion 27 and clamping portions 28 at theopposite ends thereof. Each clamping portion 28 has lugs 29 whichembrace the fuse terminals 25, 30, the lower fuse terminal 30constituted by the upper end of the conducting flexible cable 21.

As mentioned, soldering operations are performed at each clamping end 28following the clamping of the lugs 29 about the cables 21, 24. Theflexible leads or cables 24, 21 may be formed of a plurality of tinnedcopper strands.

Soldered to the clamping portions 8, at opposite ends of the strain clip26, is a fuse 31, more clearly shown in Figs. 8 and 9 of the drawings.Preferably the fuse 31 has a bend 32 formed therein so that the entirestrain will be taken by the strain clip 26, and not by the fuse 31. Asshown in Fig. 4, it will be noted that with the construction used, thelower sides of the clamping portions 28 of the strain clip 26 formsuitable surfaces 33, to which the ends 34 of the fuse 31 may besoldered.

With the construction shown, upon a fault condition occurring in thecircuit, the fuse 31 and the strain-strap portion 27 of the strain clip26 will be fused substantially simultaneously, to thereby permit thehelical spring 18 of the cut-out 1 to withdraw the cable 21 and thelower fuse terminal 30 from the open lower end of the fuse tube 22. Theare established between the fuse terminals 25, 30 will be brought intoengagement with the gas-evolving material of the inner fuse tube 22b.The turbulent evolution of gas from the inner fuse tube 22b will passthrough the drawn arc and eject the lower fuse terminal 30 out of thelower end of the fuse tube 22 to rapidly extinguish the lengthening arc.

During the occurrence of light overloads of a continuing nature, whichmay be harmful to the apparatus protected by the fuse link 10, the fuse31, which normally carries most of the current, will fuse first, therebyforcing the total current to pass through the high-resistance strainclip 26 through the strain-strap portion 27 thereof.

The result will be a fusion of the strain-strap portion 27, which willthereby permit the spring 18 to withdraw the lower fuse terminal 30 outof the fuse tube 22, as before, with are extinction taking place in asimilar manner.

It will be observed that the strain clip 26 is easily blanked out ineconomical fashion, and may be readily formed. Moreover, the expansiveareas 33 of the clamping portions 28 provide a secure grip upon thecables 21,

'24 when the strain clip 26 is clamped thereto. Also, the

aforesaid expansive areas 33 provide considerable soldering area betweenthe clamping portions 28 and the cables 21, 24. Further, the saidexpansive areas 33 provide good :seats for the ends of the fuse 31 to besoldered thereto, as indicated in Fig. 4 of the drawings. The result isa strong strain-wire fuse-link construction, in which hightensilestrength is achieved in the strain element, with no chance of mechanicalbreakage under normal conditions.

In the modification of my invention illustrated in Figs. -12, it will beobserved, with particular attention being directed to Fig. "10 thereof,that a fuse holder 35 is provided, having an upper terminal ferrule 36and a lower terminal collar 37. The terminal ferrule 36 is preferablythreadedly secured to the upper end of the fuse tube 38,

4 as at 39. A set screw 40 secures the terminal collar 37 rigidly inplace adjacent the lower end of the fuse tube 38.

The fuse-refill unit, generally designated by the reference character 41in Figs. 11 and 12, is passed downwardly interiorly within the fuse tube38, as shown in Fig. 10, with the head 42 thereof clamped between thetop of the terminal ferrule 36 and a terminal cap 43, the latter beingthreadedly secured to an upper extension 44 of the ferrule 36. The lowerend of the cable, or tail, 45 is secured by a set screw 46, having aknurled head, to the terminal collar 37.

As Well known by those skilled in the art, the terminal ferrule 36 andthe terminal collar 37 electrically and mechanically engage suitablefuse clips, not shown, connect ing thereby the fuse holder 35 into thecircuit to be protected.

Referring more particularly to Figs. 11 and 12, it will be observed thatthe head 42 has a lower depending rodshaped portion 47 constituting afuse terminal which is embraced by the clamping portion 48 of a strainclip 49, the configuration of the blank form of which is more clearlyshown in Fig. 11A of the drawings.

In a manner similar to that heretofore described in connection with Fig.5, the strain clip 49 is blanked out, as shown in Fig. 11A. Preferably,it is formed from a suit able high-resistance material such as acopper-nickel alloy. As mentioned, one clamping portion 48 thereof iscrimped to the rod portion 47 of the head 42, and is soldered theretofollowing such crimping operation. The other clamping portion 48 iscrimped and soldered to the fuse terminal end 50 of the flexibleconducting cable 45.

Situated between the lower terminal end 52 of the rod portion 47 of thehead 42 and the upper end 53 of the cable 45 is a fuse 54 having a bend55 (Fig. 11). The fuse 54 is soldered into place upon the clampingportions 48 of the strain clip 49.

Following such operations, an enclosing tube 56 is slipped over thecable 45 in the manner shown in Fig. 11. At least the inner surface ofthe tube 56 is of a material which will evolve an arc-extinguishing gaswhen contacted .by an electric arc.

The complete assembly of the fuse-refill unit 41 within a fuse holder 35is depicted in Fig. 10. During heavy overload conditions, or undershort-circuit situations, the fuse 54 and the strain-strap portion 57 ofthe strain clip 49 will be disintegrated, substantially simultaneously.The resulting are established between the fuse terminals 52, 50 willcontact the inner wall of the fuse tube 56, thereby evolving aconsiderable quantity of gas. The pressure of such evolved gas willforcibly eject the lower fuse terminal 50 and the cable 45 out of theopen lower end of the fuse tube 56, the cable 45 hanging downwardly fromthe terminal collar 37 indicating thereby a blown condition of the fuse.

During light continuing overloads of a harmful nature, the fuse 54 willfirst fuse, thereby forcing the total current to pass through thestrain-strap portion 57 of the strain clip 49. Since the strain clip 49is formed of a relatively high-resistance material, it will soon fuse,thereby establishing an arc between the fuse terminals 50, 52. Gasevolution and are extinction occur as in the same manner described inconnection with short-circuit conditions.

From the foregoing constructions, it will be apparent that I haveprovided an improved and highly effective fuse-link constructioninvolving an improved strainwire construction. The strain clips 26, 49are mechanically strong, easily and economically manufactured, and arehighly resistant to mechanical failure under normal operatingconditions. An application of my invention to fusible interruptingdevices eliminates the uncertainty of faulty operation of the prior-artstrain elements. Moreover, with the constructions which I disclose, .itwill be apparent that there is considerable soldering and crimp ing areainvolved, so that there is no likelihood of soldering connectionsbreaking or of cables pulling loose. In addition, it will be noted thatthe construction is compact, and easily assembled into a completefuse-refill unit.

Although I have shown and described specific structures, it is to beclearly understood that the same were merely for the purpose ofillustration, and that changes and modifications may be readily made, bythose skilled in the art, without departing from the spirit and scope ofthe invention.

I claim as my invention:

1. A fusible interrupting device wherein a fuse link assemblyelectrically interconnects a pair of spaced fuse terminals and whereinoverload protection is obtained by fusion of the fuse link assembly,characterized by the combination of a strain element composed ofconducting sheet material through which current may pass, an elongatedfuse secured adjacent the ends of the strain element in electricalparallel thereto, the conducting strain element having at least onewidened clamping end portion embracingly clamping the inner end of oneof the fuse terminals, said widened clamping end portion being anintegral part of the strain element and formed of the same conductingsheet material as the strain element, and the current passing throughthe strain element after the fuse melts.

2. A fusible interrupting device wherein a fuse link assemblyelectrically interconnects a pair of spaced fuse terminals and whereinoverload protection is obtained by fusion of the fuse link assembly,characterized by the combination of a strain element composed ofconducting sheet material through which current may pass, an elongatedfuse secured adjacent the ends of the strain element in electricalparallel thereto, the conducting strain element having at least one endcrimped to one fuse terminal, said one end of the conducting strainelement being an integral part of the strain element and formed of thesame conducting sheet material as the strain element, and the currentpassing through the strain element after the fuse melts.

References Cited in the file of this patent UNITED STATES PATENTS1,226,151 Weinberg May 15, 1917 1,663,333 Carmean Mar. 20, 19282,043,024 Williams June 2, 1936 2,050,277 Crabbs et al. Aug. 11, 19362,056,760 Austin Oct. 6, 1936 2,172,226 Smith Sept. 5, 1939 2,174,767Triplett et a1. Oct. 3, 1939 2,208,440 Williams July 16, 1940 2,250,210Smith July 22, 1941 2,324,044 Tripplett et al July 13, 1943 2,394,590Boothe Feb. 12, 1946 2,493,601 Smith Jan. 3, 1950 2,563,566 Von HoornAug. 7, 1951 2,640,128 Fahnoe et a1. May 26, 1953 FOREIGN PATENTS185,889 Great Britain Sept. 21, 1922 UNITED STATES PATENT OFFICECERTIFICATE OF CORRECTION Patent No. 2,821,604 January 28, 1958 James M.Wallace I It is hereby certified the requiring correction and that tbelow.

t error appears in the above numbered patent he said Letters Patentshould read as corrected In the drawin gs, Sheet 4 should be canceled;l, 2 and 3,

in the heading to Sheets line 3, for "4 Sheets" each occurrence, read--3 Sheets--. Signed and sealed this 29th day of April 1958.

SEAL) Atfiest:

KARL H. AXLINE ROBERT C. WATSON Attestlng Officer Comnissioner ofPatents UNITED STATES PATENT OFFICE January 28, 1958 James M. Wallace IIt is hereby certif' requiring correction and that the said L below,

In the drawi ngs, Sheet 4 should 1, 2 and 3,

be canceled; line 3, for "4 Sheets" each occurrence Signed and sealedthis 29th day of April 1958.

in the heading to Sheets read --3 Sheets--.

(SEAL) Attest:

KARL H. AXLINE ROBERT C. WATS N Attesting Officer 0 Conmissioner ofPatents

